
#include "inflate_lzma.h"

#include <cstdio>
#include <cstring>
#include <cerrno>
#ifndef LZMA_API_STATIC
#define LZMA_API_STATIC
#endif
#include <lzma.h>

// The following code is from the liblzma example:
// https://github.com/tukaani-project/xz/blob/master/doc/examples/02_decompress.c
static bool init_decoder(lzma_stream* strm)
{
    // Initialize a .xz decoder. The decoder supports a memory usage limit
    // and a set of flags.
    //
    // The memory usage of the decompressor depends on the settings used
    // to compress a .xz file. It can vary from less than a megabyte to
    // a few gigabytes, but in practice (at least for now) it rarely
    // exceeds 65 MiB because that's how much memory is required to
    // decompress files created with "xz -9". Settings requiring more
    // memory take extra effort to use and don't (at least for now)
    // provide significantly better compression in most cases.
    //
    // Memory usage limit is useful if it is important that the
    // decompressor won't consume gigabytes of memory. The need
    // for limiting depends on the application. In this example,
    // no memory usage limiting is used. This is done by setting
    // the limit to UINT64_MAX.
    //
    // The .xz format allows concatenating compressed files as is:
    //
    //     echo foo | xz > foobar.xz
    //     echo bar | xz >> foobar.xz
    //
    // When decompressing normal standalone .xz files, LZMA_CONCATENATED
    // should always be used to support decompression of concatenated
    // .xz files. If LZMA_CONCATENATED isn't used, the decoder will stop
    // after the first .xz stream. This can be useful when .xz data has
    // been embedded inside another file format.
    //
    // Flags other than LZMA_CONCATENATED are supported too, and can
    // be combined with bitwise-or. See lzma/container.h
    // (src/liblzma/api/lzma/container.h in the source package or e.g.
    // /usr/include/lzma/container.h depending on the install prefix)
    // for details.
    lzma_ret ret = lzma_stream_decoder(strm, UINT64_MAX, LZMA_CONCATENATED);

    // Return successfully if the initialization went fine.
    if (ret == LZMA_OK)
        return true;

    // Something went wrong. The possible errors are documented in
    // lzma/container.h (src/liblzma/api/lzma/container.h in the source
    // package or e.g. /usr/include/lzma/container.h depending on the
    // install prefix).
    //
    // Note that LZMA_MEMLIMIT_ERROR is never possible here. If you
    // specify a very tiny limit, the error will be delayed until
    // the first headers have been parsed by a call to lzma_code().
    const char* msg;
    switch (ret) {
        case LZMA_MEM_ERROR:
            msg = "Memory allocation failed";
            break;

        case LZMA_OPTIONS_ERROR:
            msg = "Unsupported decompressor flags";
            break;

        default:
            // This is most likely LZMA_PROG_ERROR indicating a bug in
            // this program or in liblzma. It is inconvenient to have a
            // separate error message for errors that should be impossible
            // to occur, but knowing the error code is important for
            // debugging. That's why it is good to print the error code
            // at least when there is no good error message to show.
            msg = "Unknown error, possibly a bug";
            break;
    }

    fprintf(stderr, "Error initializing the decoder: %s (error code %u)\n", msg, ret);
    return false;
}

static bool decompress(lzma_stream* strm, const char* inname, FILE* infile, FILE* outfile)
{
    // When LZMA_CONCATENATED flag was used when initializing the decoder,
    // we need to tell lzma_code() when there will be no more input.
    // This is done by setting action to LZMA_FINISH instead of LZMA_RUN
    // in the same way as it is done when encoding.
    //
    // When LZMA_CONCATENATED isn't used, there is no need to use
    // LZMA_FINISH to tell when all the input has been read, but it
    // is still OK to use it if you want. When LZMA_CONCATENATED isn't
    // used, the decoder will stop after the first .xz stream. In that
    // case some unused data may be left in strm->next_in.
    lzma_action action = LZMA_RUN;

    uint8_t inbuf[BUFSIZ];
    uint8_t outbuf[BUFSIZ];

    strm->next_in = nullptr;
    strm->avail_in = 0;
    strm->next_out = outbuf;
    strm->avail_out = sizeof(outbuf);

    while (true) {
        if (strm->avail_in == 0 && !feof(infile)) {
            strm->next_in = inbuf;
            strm->avail_in = fread(inbuf, 1, sizeof(inbuf), infile);

            if (ferror(infile)) {
                fprintf(stderr, "%s: Read error: %s\n", inname, strerror(errno));
                // SonarCloud: Address of stack memory associated with local
                // variable 'inbuf' is still referred to by the stack variable
                // 'strm' upon returning to the caller. This will be a
                // dangling reference
                // Fixed by setting to nullptr.
                strm->next_in = nullptr;
                strm->avail_in = 0;
                strm->next_out = nullptr;
                strm->avail_out = 0;
                return false;
            }

            // Once the end of the input file has been reached,
            // we need to tell lzma_code() that no more input
            // will be coming. As said before, this isn't required
            // if the LZMA_CONCATENATED flag isn't used when
            // initializing the decoder.
            if (feof(infile))
                action = LZMA_FINISH;
        }

        lzma_ret ret = lzma_code(strm, action);

        if (strm->avail_out == 0 || ret == LZMA_STREAM_END) {
            size_t write_size = sizeof(outbuf) - strm->avail_out;

            if (fwrite(outbuf, 1, write_size, outfile) != write_size) {
                fprintf(stderr, "Write error: %s\n", strerror(errno));
                strm->next_in = nullptr;
                strm->avail_in = 0;
                strm->next_out = nullptr;
                strm->avail_out = 0;
                return false;
            }

            strm->next_out = outbuf;
            strm->avail_out = sizeof(outbuf);
        }

        if (ret != LZMA_OK) {
            // Once everything has been decoded successfully, the
            // return value of lzma_code() will be LZMA_STREAM_END.
            //
            // It is important to check for LZMA_STREAM_END. Do not
            // assume that getting ret != LZMA_OK would mean that
            // everything has gone well or that when you aren't
            // getting more output it must have successfully
            // decoded everything.
            if (ret == LZMA_STREAM_END) {
                strm->next_in = nullptr;
                strm->avail_in = 0;
                strm->next_out = nullptr;
                strm->avail_out = 0;
                return true;
            }

            // It's not LZMA_OK nor LZMA_STREAM_END,
            // so it must be an error code. See lzma/base.h
            // (src/liblzma/api/lzma/base.h in the source package
            // or e.g. /usr/include/lzma/base.h depending on the
            // install prefix) for the list and documentation of
            // possible values. Many values listen in lzma_ret
            // enumeration aren't possible in this example, but
            // can be made possible by enabling memory usage limit
            // or adding flags to the decoder initialization.
            const char* msg;
            switch (ret) {
                case LZMA_MEM_ERROR:
                    msg = "Memory allocation failed";
                    break;

                case LZMA_FORMAT_ERROR:
                    // .xz magic bytes weren't found.
                    msg = "The input is not in the .xz format";
                    break;

                case LZMA_OPTIONS_ERROR:
                    // For example, the headers specify a filter
                    // that isn't supported by this liblzma
                    // version (or it hasn't been enabled when
                    // building liblzma, but no-one sane does
                    // that unless building liblzma for an
                    // embedded system). Upgrading to a newer
                    // liblzma might help.
                    //
                    // Note that it is unlikely that the file has
                    // accidentally became corrupt if you get this
                    // error. The integrity of the .xz headers is
                    // always verified with a CRC32, so
                    // unintentionally corrupt files can be
                    // distinguished from unsupported files.
                    msg = "Unsupported compression options";
                    break;

                case LZMA_DATA_ERROR:
                    msg = "Compressed file is corrupt";
                    break;

                case LZMA_BUF_ERROR:
                    // Typically this error means that a valid
                    // file has got truncated, but it might also
                    // be a damaged part in the file that makes
                    // the decoder think the file is truncated.
                    // If you prefer, you can use the same error
                    // message for this as for LZMA_DATA_ERROR.
                    msg = "Compressed file is truncated or "
                          "otherwise corrupt";
                    break;

                default:
                    // This is most likely LZMA_PROG_ERROR.
                    msg = "Unknown error, possibly a bug";
                    break;
            }

            fprintf(
                stderr,
                "%s: Decoder error: "
                "%s (error code %u)\n",
                inname,
                msg,
                ret);

            strm->next_in = nullptr;
            strm->avail_in = 0;
            strm->next_out = nullptr;
            strm->avail_out = 0;
            return false;
        }
    }
}

bool InflateLZMA::inflateLZMAFile(
    const std::filesystem::path& lzma_filename, const std::filesystem::path& decompressed_filename)
{
    lzma_stream strm = LZMA_STREAM_INIT;

    if (!init_decoder(&strm)) {
        // Decoder initialization failed. There's no point
        // to retry it so we need to exit.
        return false;
    }

    FILE* infile = fopen(lzma_filename.string().c_str(), "rb");

    if (infile == nullptr) {
        fprintf(
            stderr,
            "%s: Error opening the "
            "input file: %s\n",
            lzma_filename.string().c_str(),
            strerror(errno));
        return false;
    }

    FILE* outfile = fopen(decompressed_filename.string().c_str(), "wb");

    if (outfile == nullptr) {
        fprintf(
            stderr,
            "%s: Error opening the "
            "output file: %s\n",
            decompressed_filename.string().c_str(),
            strerror(errno));
        fclose(infile);
        return false;
    }

    const bool success = decompress(&strm, lzma_filename.string().c_str(), infile, outfile);
    fclose(infile);
    fclose(outfile);

    lzma_end(&strm);

    return success;
}
